Apparatus and method for preparing a canister loaded with wet radioactive elements for dry storage

Abstract

The present invention provides a method and system of preparing a canister having a cavity loaded with wet radioactive elements for dry storage, the method comprising: (a) providing a gas circulation system comprising means for removing moisture from gas; (b) connecting the gas circulation system to the canister so as to form a hermetically sealed closed-loop path that includes the cavity; and (c) circulating a non-reactive gas through the hermetically sealed closed-loop path until a desired vapor pressure is achieved in the cavity of the canister, the circulating non-reactive gas becoming wetted as the non-reactive gas flows through the canister and dried as the non-reactive gas flows through the moisture removal means. The apparatus comprises a gas circulation system comprising a source of a non-reactive gas and means for removing moisture from gas, the gas circulation system adapted to form a hermetically sealed closed-loop path when operably connected to a cavity of a canister to be prepared for dry storage; and means for circulating the non-reactive gas of the source through the closed-loop path so that the circulating non-reactive gas becomes wetted while flowing through the canister and dried as flowing through the moisture removal means.

1 . A method of preparing a canister having a cavity loaded with wet radioactive elements for dry storage, the method comprising: 
 (a) providing a gas circulation system comprising means for removing moisture from gas;    (b) connecting the gas circulation system to the canister so as to form a hermetically sealed closed-loop path that includes the cavity; and    (c) circulating a non-reactive gas through the hermetically sealed closed-loop path until a desired vapor pressure is achieved in the cavity of the canister, the circulating non-reactive gas becoming wetted as the non-reactive gas flows through the canister and dried as the non-reactive gas flows through the moisture removal means.    
     
     
         2 . The method of  claim 1  further comprising controlling and/or measuring at least one psychrometric property of the non-reactive gas along the closed-loop path at a location outside of the cavity to ensure that the desired vapor pressure is achieved in the cavity.  
     
     
         3 . The method of  claim 2  wherein the controlled and/or measured psychrometric property can be correlated to an existing vapor pressure within the cavity of the canister via a psychrometric relationship.  
     
     
         4 . The method of  claim 3  further comprising, upon the controlled and/or measured thermodynamic property being indicative that the existing vapor pressure within the cavity of the canister is at or below the desired vapor pressure, ceasing the circulation of the non-reactive gas through the hermetically sealed closed-loop path.  
     
     
         5 . The method of  claim 1  further comprising: 
 upon the desired vapor pressure being achieved in the cavity, ceasing the circulation of the non-reactive gas through the hermetically sealed closed-loop path;    disconnecting the gas circulation system from the canister; and    sealing the cavity thereby forming an atmosphere of the non-reactive gas within the cavity.    
     
     
         6 . The method of  claim 1  wherein the gas circulation system further comprises a source of the non-reactive gas.  
     
     
         7 . The method of  claim 1  wherein the gas is nitrogen, carbon dioxide, light hydrocarbon gases, or an inert gas selected from the group consisting of helium, argon, krypton and xenon.  
     
     
         8 . The method of  claim 1  wherein the canister is vertically oriented and located within an overpack module during steps (a) through (c).  
     
     
         9 . The method of  claim 1  further comprising: 
 controlling and/or measuring at least one psychrometric property of the non-reactive gas along the closed-loop path at a location outside of the cavity, the controlled and/or measured psychrometric property capable of being correlated to an existing vapor pressure within the cavity of the canister;    upon the controlled and/or measured psychrometric property being indicative that the existing vapor pressure within the cavity of the canister is at or below a desired vapor pressure, ceasing the circulation of the non-reactive gas through the hermetically sealed closed-loop path; and    sealing the cavity thereby forming an atmosphere of the non-reactive gas within the cavity.    
     
     
         10 . The method of  claim 9  wherein the desired vapor pressure is at or below 3 Torrs and the gas is nitrogen, carbon dioxide, light hydrocarbon gases, or an inert gas selected from the group consisting of helium, argon, krypton and xenon.  
     
     
         11 . The method of  claim 9  wherein the controlled and/or measured psychrometric property is temperature.  
     
     
         12 . The method of  claim 9  further comprising measuring at least one psychrometric property of the non-reactive gas along the closed-loop path at a location outside of the cavity, the measured psychrometric property capable of being correlated to an existing vapor pressure within the cavity of the canister through the use of a psychrometric relationship.  
     
     
         13 . A method of drying a canister loaded with wet radioactive elements comprising: 
 (a) providing a gas circulation system comprising a source of a non-reactive gas and a means for removing moisture from gas;    (b) connecting the gas circulation system to the canister so as to form a closed-loop fluid path;    (c) flowing the non-reactive gas through the canister, the non-reactive gas exiting the canister as wet non-reactive gas that flows into the moisture removal means;    (d) removing moisture from the wet non-reactive gas via the moisture removal means to create a dried non-reactive gas;    (e) flowing the dried non-reactive gas through the canister; and    (f) continuing step (c) through (d) until a desired vapor pressure is achieved in the canister.    
     
     
         14 . The method of  claim 13  further comprising: 
 controlling and/or measuring at least one psychrometric property of the non-reactive gas along the closed-loop path at a location outside of the canister, the controlled and/or measured psychrometric property capable of being correlated to an existing vapor pressure within the canister;    upon the controlled and/or measured psychrometric property being indicative that the existing vapor pressure within the cavity of the canister is at or below a desired vapor pressure, ceasing the circulation of the non-reactive gas through the hermetically sealed closed-loop path; and    sealing the canister thereby forming an atmosphere of the non-reactive gas within the cavity.    
     
     
         15 . An apparatus for preparing a canister having a cavity loaded with radioactive elements for dry storage, the apparatus comprising: 
 a gas circulation system comprising a source of a non-reactive gas and means for removing moisture from gas, the gas circulation system adapted to form a hermetically sealed closed-loop path when operably connected to a cavity of a canister to be prepared for dry storage; and    means for circulating the non-reactive gas of the source through the closed-loop path so that the circulating non-reactive gas becomes wetted while flowing through the canister and dried as flowing through the moisture removal means.    
     
     
         16 . The apparatus of  claim 15  further comprising sensor means operably coupled to the closed-loop path at a location outside of the cavity for measuring a psychrometric property of the non-reactive gas flowing through the closed-loop path, the psychrometric property capable of being correlated to an existing vapor pressure within the cavity of the canister through a psychrometric relationship.  
     
     
         17 . The apparatus of  claim 15  wherein the gas circulation system further comprises means to heat the non-reactive gas flowing through the closed-loop path, the heating means loaded downstream of the moisture removal means.  
     
     
         18 . The apparatus of  claim 15  wherein the moisture removal means comprises a condenser module fluidly coupled upstream to a demoisturizer module, the demoisturizer module adapted to freeze the non-reactive gas flowing through the closed-loop path.  
     
     
         19 . The apparatus of  claim 15  wherein the source of the non-reactive gas is a source of nitrogen, carbon dioxide, light hydrocarbon gases, or an inert gas selected from the group consisting of helium, argon, krypton, and xenon.  
     
     
         20 . The apparatus of  claim 15  wherein the circulating means comprises a gas circulator.  
     
     
         21 . An apparatus for preparing a canister having a cavity loaded with radioactive elements for dry storage, the apparatus comprising: 
 a gas circulation system comprising a source of a non-reactive gas, means for removing moisture from gas, sensor means for measuring a psychrometric property of gas and means for circulating gas; and    wherein the gas circulation system is adapted to (1) form a hermetically sealed closed-loop path when operably connected to a cavity of a canister to be prepared for dry storage, (2) circulate the non-reactive gas through the closed-loop path so that the non-reactive gas becomes wetted flowing through the cavity of the canister and dried flowing through the moisture removal means; and (3) achieve a desired vapor pressure within the cavity of the canister based on measurements of the sensor means and a psychrometric relationship.